User Manual:HDAudioPassthrough

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MythTV trunk from December 5th 2010 supports HD audio passthrough

Those are preliminary information on how to enable HD audio passthrough over HDMI (currenly E-AC3, DTS-HD Hi-Res, TrueHD and DTS-HD MA).

Not all video cards are equals. You need a video card with built-in audio chipset, and hdmi port. Additionally, for TrueHD and DTS-HD MA it has support to HBR (high bit-rate).

Dolby Digital Plus (E-AC3) and DTS-HD Hi-Res

To support DD+ and DTS-HD HR ; your audio card must support stereo output at 192kHz.

Audio/Video cards known to support it:

  • ION and 9400M IGP : provided you use a kernel newer than 2.6.32 (it is not supported in kernel 2.6.31 and earlier)
  • ION2
  • nVidia GT2xx
  • nVidia GT4xx
  • nVidia GT5xx
  • Some Intel HDMI graphics chipsets (in particular IbexPeak (0x80862804), CougarPoint)

Audio/Video cards known not to support it

  • Most ATI card (many only support 48kHz)
  • Intel HDMI graphics chipsets Cantiga, Eaglelake

To check for actual support, run mythfrontend and go into Setup -> Audio. If the E-AC3/DTS-HD flag is enabled, it is likely that your audio card supports it. Remember you must use an HDMI connection. Optical or coaxial SPDIF will *not* work.

TrueHD and DTS-HD MA support

For your audio card to support loss-less HD audio passthrough (TrueHD and DTS-HD MA), your audio card has to support HBR You can check DTS-HD/TrueHD support on Linux by checking for "HBR" text in "Pincap" line in /proc/asound/cardX/codec#Y

Chips known *not* to support HBR:

  • ION first generation
  • nVidia 9400M IGP
  • nVidia 8xxx, 9xxx

Chips known to support HBR:

  • ION2
  • nVidia GT4xx
  • nVidia GT5xx

Though not officially supported, HBR works to some extent with nVidia GT2xx ; your mileage may vary. It is highly dependent of the combination between audio processor/amplifier and video card.

You'll need a recent linux kernel (>= 2.6.36) that contains the required ALSA drivers.


Alternatively get the latest ALSA driver from the git repository

git clone git://git.alsa-project.org/alsa-driver.git alsa-driver 
git clone git://git.alsa-project.org/alsa-kmirror.git alsa-kmirror 
cd alsa-driver
./gitcompile
sudo make install

Alsa library 1.0.23 is the required minimum. However if you had to mess with the device name to get basic audio working, it is strongly recommended you get a new version as otherwise you will likely have to mess with alsa configuration file.

git clone git://git.alsa-project.org/alsa-lib.git alsa-lib
cd alsa-lib
./git-compile
sudo make install